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Background: In ergonomic risk assessment of hand-intensive work, observational methods are typically used to rate risk exposure. However, it remains unclear whether women and men performing identical work tasks are rated differently with respect to the established risk exposures: hand activity/repetitivity and hand force. To better understand these ratings, measured wrist joint angular velocity and measured forearm muscle activity could be examined in parallel.

Aim: The aim was threefold: (1) to investigate whether hand activity (Hand Activity Level, HAL) and hand force (Borg CR-10) are rated differently between women and men performing identical work tasks; (2) to compare technically measured wrist angular velocity and measured forearm muscle activity between female and male workers; and (3) to examine the correlations between these ratings and their corresponding technical data.

Methods: Fifty-nine workers (29 women, 30 men), organized into 28 female–male pairs, participated. Each pair performed identical hand-intensive tasks across different real-world workplaces. Data were collected on workers’ measured wrist joint angular velocity (°/s) using inertial measurement units and on flexor and extensor carpi radialis (FCR, ECR) muscle activity and recovery, expressed as a percentage of maximal voluntary electrical activation (%MVE), via surface electromyography. Workers' self-rated hand activity level (HAL) and hand force (Borg CR-10). All tasks were video recorded. Additionally, two mixed-gender pairs of experienced ergonomists (n = 4) and 54 individual ergonomists (27 women, 27 men) video-rated the workers’ tasks using the HAL and Borg CR-10 scales. Analyses included sex-based comparisons of all variables and correlations between ratings (self and ergonomist-rated) and technical measures. In Paper I, differences in HAL and Borg CR-10 ratings between female and male workers were compared using self-ratings and ratings from mixed-gender ergonomist pairs. Paper II examined correlations between wrist angular velocity and HAL, and between forearm muscle activity and Borg CR-10. Paper III compared measured wrist angular velocity and muscle activity between women and men. Paper IV analyzed individual ergonomist ratings in 27 female–male pairs with similar professional experience to determine whether female and male workers were rated differently (HAL, Borg CR-10.

Results: No significant sex differences were found in wrist velocity (Paper III) or HAL ratings, whether self-rated, rated by ergonomist pairs, or individual ergonomists (Papers I and IV). Self-rated HAL (tau = 0.23–0.31, p = 0.002–0.005) and ergonomist pair ratings (tau = 0.32–0.41, p = 0.001) correlated significantly with wrist velocity. Measured FCR and ECR muscle activity were significantly higher in women than men (p = 0.004–<0.001) (Paper III). Similarly, ergonomist-rated hand force (Borg CR-10) was significantly higher for female workers, both in pair ratings (women: 3.9 ± 2.7; men: 3.1 ± 1.8, p = 0.01) and individual ratings (mean difference 0.35, p < 0.001) (Papers I and IV). In contrast, workers’ self-rated hand force did not differ significantly between women and men (Paper I). Measured FCR and ECR muscle activity and ergonomist-rated hand force correlated significantly in 4 of 6 variables (tau = 0.32–0.41, p = 0.01–<0.001), and for recovery time in FCR only (tau = –0.47, p = 0.001) (Paper II). In contrast, self-rated hand force did not correlate significantly with measured muscle activity (Paper II).

Conclusions: Measured wrist velocity and HAL ratings show no systematic differences between women and men performing identical work tasks. Women’s higher measured muscle activity and higher ergonomist-rated hand force (Borg CR-10) indicate that these methods detect sex differences. Therefore, when ratings are used, ergonomist-rated hand force should be prioritized. In contrast, self-rated hand force using the Borg CR-10 does not detect sex differences and may underestimate women’s hand force. Therefore, self-ratings should be avoided in risk assessments aiming to capture sex-based differences. Due to limitations in subjective ratings, technical measures should be preferred when possible. When tasks are identical, women should be prioritized in assessments of hand force or muscle activity to ensure protection for all workers. These strategies may help detect sex differences in hand force and improve precision in risk assessment. This can support the protection of both women and men in hand-intensive work from musculoskeletal disorders and promote a sustainable working life.